Alligatorinae is a subfamily within the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Alligatoridae The family Alligatoridae of crocodylians includes alligators, caimans and their extinct relatives. Phylogeny The superfamily Alligatoroidea includes all crocodilians (fossil and extant) that are more closely related to the American alligator ...

that contains the

alligators An alligator is a large reptile in the Crocodilia order in the genus ''Alligator'' of the family Alligatoridae. The two extant species are the American alligator (''A. mississippiensis'') and the Chinese alligator (''A. sinensis''). Additionall ...

and their closest extinct relatives, and is the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

Caimaninae A caiman (also cayman as a variant spelling) is an alligatorid belonging to the subfamily Caimaninae, one of two primary lineages within the Alligatoridae family, the other being alligators. Caimans inhabit Mexico, Central and South America fr ...

(the caimans). Many genera in Alligatorinae are described, but only the genus ''

Alligator An alligator is a large reptile in the Crocodilia order in the genus ''Alligator'' of the family Alligatoridae. The two extant species are the American alligator (''A. mississippiensis'') and the Chinese alligator (''A. sinensis''). Additiona ...

'' is still living, with the remaining genera extinct.

Evolution

Alligators An alligator is a large reptile in the Crocodilia order in the genus ''Alligator'' of the family Alligatoridae. The two extant species are the American alligator (''A. mississippiensis'') and the Chinese alligator (''A. sinensis''). Additionall ...

and

caimans A caiman (also cayman as a variant spelling) is an alligatorid belonging to the subfamily Caimaninae, one of two primary lineages within the Alligatoridae family, the other being alligators. Caimans inhabit Mexico, Central and South America fr ...

split in North America during the early

Tertiary Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...

or late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

(about 53 million to about 65 million years ago). The Chinese alligator split from the

American alligator The American alligator (''Alligator mississippiensis''), sometimes referred to colloquially as a gator or common alligator, is a large crocodilian reptile native to the Southeastern United States. It is one of the two extant species in the gen ...

about 33 million years ago and likely descended from a lineage that crossed the Bering land bridge during the Neogene. The modern American alligator is well represented in the fossil record of the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...

. The alligator's full

mitochondrial genome Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial ...

was sequenced in the 1990s. The full

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding g ...

, published in 2014, suggests that the alligator evolved much more slowly than mammals and birds.

Phylogeny

Alligatorinae is

cladistically Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

defined as ''Alligator mississippiensis'' (the

) and all species closer to it than to ''Caiman crocodylus'' (the spectacled caiman). This is a stem-based definition for Alligatorinae, and means that it includes more basal extinct alligator ancestors that are more closely related to living alligators than to

. The below

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

shows the

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spe ...

of Alligatorinae.

Taxonomy

* Subfamily Alligatorinae ** Genus ''

'' *** † ''

Alligator hailensis ''Alligator hailensis'', or Haile alligator, is a large, extinct species of ''Alligator'' known from the early Pleistocene of Florida. It is named after the town of Haile, Florida, where it was found. Its age and skeletal morphology is intermed ...

'' *** † '' Alligator mcgrewi'' *** † ''

Alligator mefferdi ''Alligator mefferdi'' is an extinct species of alligator described by Charles Craig Mook. They lived in the Miocene period, and their range was principally in what is now Nebraska, United States.American alligator The American alligator (''Alligator mississippiensis''), sometimes referred to colloquially as a gator or common alligator, is a large crocodilian reptile native to the Southeastern United States. It is one of the two extant species in the gen ...

*** † ''

Alligator olseni ''Alligator olseni'' (common name Olsen's Alligator, named after Russel Olsen) is an extinct species of alligator. They lived in the Early Miocene period, around 20.4–15.97 million years ago and possibly earlier. Their range was principally in ...

'' *** † ''

Alligator prenasalis ''Alligator prenasalis'' is an extinct species of alligator from the Late Eocene period. It is well known, with many fossils having been collected from the Chadron and Brule Formations in South Dakota. The species was first named in 1904, but wa ...

'' *** ''Alligator sinensis'', Chinese alligator *** † '' Alligator thomsoni'' ** Genus † '' Allognathosuchus'' ** Genus † '' Arambourgia'' ** Genus † '' Ceratosuchus'' ** Genus † '' Chrysochampsa'' ** Genus † '' Eoalligator'' ** Genus † '' Hassiacosuchus'' ** Genus † '' Krabisuchus'' ** Genus † '' Navajosuchus''? ** Genus † '' Procaimanoidea'' ** Genus † '' Wannaganosuchus''

References

Alligatoridae Selandian first appearances Extant Paleocene first appearances Taxa named by John Edward Gray Tetrapod subfamilies {{archosaur-stub